Heat affects learning, especially for black and Hispanic students. They face hotter days and classrooms amid climate change and earlier school starts.

For millions of American kids, going back to school is an exciting time of reconnecting with friends, learning about new ideas and engaging fresh possibilities. But for too many of them, particularly racial minorities living in low-income neighborhoods, the excitement of learning is curbed by sweltering classrooms with little or no air conditioning.

This is not merely a question of discomfort. Rather, our research suggests that overheated classrooms contribute to racial achievement gaps by lessening learning in a way that adds up over time and could affect future earnings potential. At a moment when questions of race, climate and economic equity are being debated everywhere, including on the campaign trail, we should not ignore the fact that climate-proofing schools now could help students learn better and realize greater economic opportunities for decades to come.

Using data from over 12,000 schools and 10 million middle- and high-school students across America, my colleagues and I found that students who experience more hot days during the school year perform worse on subsequent standardized exams. A 1 degree hotter-than-average academic year reduces learning by about 1%.

A newly air conditioned classroom in Bement, Illinois, in 2013.(Photo: David Mercer/AP)

The effects of heat on learning are more pronounced for African-American and Hispanic students and for those living in poorer neighborhoods. School air conditioning is unequally distributed: Black and Latino students are significantly more likely to report inadequate air conditioning. For them, a 90 degree school day has a negative effect on learning that is nearly 2 1/2 times what it is for white students.

Over the years, this adds up. Just as small monthly savings can add up over many years, small disruptions to learning can accumulate into sizable disadvantages over time. Our data suggests that up to 7% of racial achievement gaps can be attributed to the combined influence of more hot days and hotter classrooms for African-American and Hispanic students.

Improving school facilities by adding air conditioning helps considerably. Based on the first nationwide school air conditioning survey, we estimate a school that has air-conditioned classrooms suffers less than a quarter of the learning losses that a school without air conditioning does.

Air conditioning is worth the cost

Building on work by other economists who link learning gains to later life earnings, we estimate that returns on cooling schools could be well worth the cost. In hot places such as Houston and Atlanta, each additional year of sufficient school air conditioning could boost collective future earnings by up to $2 million in any given high school of 1,000 students.

What’s stopping us from installing air conditioners in every classroom? Much of it comes down to funding. Over 80% of capital outlays are financed locally, usually via property taxes. Low-income areas often lack the budget to cool schools. Some states, including Hawaii, Massachusetts and California, provide considerable support. Others, including Louisiana, Michigan and Wisconsin, contribute next to none. Notably absent is federal funding. Washington contributes essentially zero dollars to improving or maintaining school facilities.

This is shortsighted. We estimate that providing adequate air conditioning and ventilation to all students could narrow the racial achievement gap by nearly a fifth of the total progress that has been made over the past four decades. Think about that: 20% of all of the equity gains achieved through dozens of initiatives aimed at closing racial gaps in educational achievement could be realized simply by improving school facilities through better climate control.

You might be thinking, “But doesn’t air conditioning contribute to climate change?” The answer depends on energy sources. Air conditioning powered by clean, renewable energy does not threaten climate stability. And given that a 2 degree Celsius rise in average temperatures could decrease learning by about 10% annually, cooling schools is an urgent matter of climate resilience.

So we must stop thinking about climate mitigation and climate adaptation as an either-or proposition. We need to do both: by putting a price on carbon and ensuring that disadvantaged populations have the capacity to cope.

Ultimately, we must recognize that adapting to climate change is a matter of racial and economic justice, especially in schools. Whether through the "Green New Deal," federal infrastructure policy or other initiatives, keeping students cool could be a cost-effective way to boost climate resilience, promote learning and economic mobility, and narrow the gap between our nation’s haves and have-nots.

Environmental economist R. Jisung Park is an assistant professor of public policy at UCLA and associate director of economic research at UCLA’s Luskin Center for Innovation. His paper Heat and Learning, co-authored with Joshua Goodman of Brandeis University, Mike Hurwitz of the College Board and Jonathan Smith of Georgia State University, has been accepted for publication in the American Economic Journal: Economic Policy. Follow Park on Twitter: @rjisungpark